Subject Experts Solutions for Exercise 2: HOTS HIGHER ORDER THINKING SKILLS

A scientist was studying an in vitro eukaryotic transcription system, which produced both capped and uncapped mRNAs. For an experiment, he incubated these mRNAs with mammalian cell nuclear extract and quantified the different products as shown. Which of the following graphs represents the expected result correctly?

A $\mathrm{DNA}$ template plus primer with the structure

$3^{\text{'}}\overline{)\mathrm{P}}-\mathrm{TGCGAATTAGCGACAT}-\overline{)\mathrm{P}}{5}^{\text{'}}$

$5^{\text{'}}\overline{)\mathrm{P}}-\mathrm{ATCGGTACGACGCTTAAC}-\mathrm{OH}{3}^{\text{'}}$

(where $\overline{)\mathrm{P}}$ a phosphate group) is placed in an in vitro DNA synthesis system containing Mg2+, an excess of the four deoxyribonucleoside triphosphates, etc., and a mutant form of E.coli DNA polymerase I that lacks $5^{\text{'}}\to 3^{\text{'}}$ exonuclease activity. The $5^{\text{'}}\to 3^{\text{'}}$ polymerase and $3^{\text{'}}\to 5^{\text{'}}$ exonuclease activities of these aberrant enzymes are identical to those of normal E. coli $\mathrm{DNA}$  polymerase $\mathrm{I}$. It simply has no $5^{\text{'}}\to 3^{\text{'}}$ exonuclease activity. What will be the structure of the final product?

$\mathrm{C}$-value is the characteristic $\mathrm{DNA}$ content in a haploid cell of a given species. Earlier it was considered that $\mathrm{C}$-value correlates with organism complexity. However, it is now evident that $\mathrm{C}$-value varies enormously among species and that this bears no correlation with the complexity of the organisms. For example, the cells of some salamanders may contain $40$ times more $\mathrm{DNA}$ than those of humans. Which of the following explains this $C$-value paradox?

The $\mathrm{DNA}$ fingerprinting analysis of four family members is shown below.

Study the band pattern obtained and assign each family member to $\mathrm{W}, \mathrm{X}, \mathrm{Y}$ and $Z$. Choose the correct option.

An organism uses $20$ amino acids while its $\mathrm{DNA}$ is made up of $6$ types of nitrogenous bases. What would be the minimum size of a codon?

The semi-conservative nature of $\mathrm{DNA}$ replication was established by Meselson and Stahl in their classic experiment with bacteria. They grew bacteria in ${\mathrm{N}}^{15}$. ${\mathrm{NH}}_4\mathrm{Cl}$ containing medium, washed and then incubated in fresh medium with ${\mathrm{N}}^{14}$- containing compounds and allowed to grow for three generations. $\mathrm{CsCl}$ density gradient centrifugation of isolated $\mathrm{DNA}$ established the nature of semiconservative $\mathrm{DNA}$ replication. The pictorial representation below shows the position of differentially labeled $\mathrm{DNA}$ in $\mathrm{CsCl}$ density gradient.

Had the $\mathrm{DNA}$ replication been conservative, what would have been the pattern?

You have created a fusion between trp operon and lac operon, which encodes the enzymes for tryptophan biosynthesis under the regulatory control of the lac operator. Under which of the following conditions will tryptophan synthase be induced in the strain that carries the chimeric operator fused operons?

A $\mathrm{DNA}$ sequence undergoes three subsequent point mutations which result in subsequent changes in transcription of $\mathrm{mRNA}$ as shown below:
Original $\mathrm{mRNA} :\mathrm{AUG} \mathrm{CAU} \mathrm{CUC} \mathrm{ACG} \mathrm{GAU} \mathrm{UAG}$

Point mutation $1 : \mathrm{AUG} \mathrm{CAU} \mathrm{CUU} \mathrm{ACG} \mathrm{GUA} \mathrm{UAG}$

Point mutation $2 : \mathrm{AUG} \mathrm{CAU} \mathrm{GCU} \mathrm{UAC} \mathrm{GGU} \mathrm{AUA}$

Point mutation $3 : \mathrm{AUG} \mathrm{CAU} \mathrm{GCU} \mathrm{UAA} \mathrm{GGU} \mathrm{AUA}$

Select the correct sequence of point mutations that occurred in the $\mathrm{DNA}$.